1. Field of the Invention
The present invention relates to a magnetic detecting device having fixed magnetic layers and a free magnetic layer, in which a magnetization direction of the fixed magnetic layers is fixed to be oriented in a particular direction, and the free magnetic layer is formed between the fixed magnetic layers via non-magnetic material layers and the magnetization direction of the free magnetic layer varies by an external magnetic field. More particularly, the present invention relates to a magnetic detecting device which is capable of increasing the product ΔRA between a magnetoresistance variation ΔR and a device area A and decreasing a ferromagnetic coupling magnetic field Hin.
2. Description of the Related Art
A magnetic detecting device has a multilayered film in which a free magnetic layer, a non-magnetic material layer, and fixed magnetic layers are laminated. In such a magnetic detecting device, there are two kinds in accordance with a difference of a current direction with respect to the multilayered film, that is, a CIP (current in the plane) type and a CPP (current perpendicular to the plane) type.
In the CIP-type magnetic detecting device, a current flows in a parallel direction to a film surface of the multilayered film. In contrast, in the CPP-type magnetic detecting device, a current flows in a perpendicular direction to the film surface of the multilayered film.
The CPP-type magnetic detecting device has an advantage in that it has a device size smaller than that of the CIP-type magnetic detecting device and increases a reproducing output. Accordingly, the CPP-type magnetic detecting device has been expected as a magnetic detecting device which can substitute for the CIP-type magnetic detecting device having been widely used and achieve a high recording density.
In the meantime, in order to allow to be put to practical use the CPP-type magnetic detecting device capable of achieving the high recording density in future, it is required to increase the product ΔRA between a magnetoresistance variation ΔR and a device area A.
Each of JP-A-2003-8102, JP-A-2002-150512, and JP-A-2004-214251 discloses a method of increasing the product ΔRA between a magnetoresistance variation ΔR and a device area A in a CPP-type magnetic detecting device.
According to a method disclosed in JP-A-2003-8102, a resistance adjusting layer is provided between a magnetization fixed layer (fixed magnetic layer) and a non-magnetic intermediate layer (non-magnetic material layer). A forming material of the resistance adjusting layer is described in claim 6 or the like in JP-A-2003-8102. Further, according to a method disclosed in JP-A-2002-150512, a free layer (free magnetic layer) is formed with a laminated structure of a thin film and a non-magnetic layer. Furthermore, according to a method disclosed in JP-A-2004-214251, unlike a fixed magnetic layer or a free layer, an inserting layer containing a semimetal is separately provided.
Although various mechanisms have been made for increasing ΔRA by using various methods including the above-mentioned methods, there is no structure which it is possible to effectively increase ΔRA such that the method can be put to practical use.
Further, in order to allow to be put to practical use the CPP-type magnetic detecting device capable of achieving the high recording density in future, it is required to decrease a ferromagnetic coupling magnetic field Hin, in addition to the increasing the ΔRA.
Since the ferromagnetic coupling magnetic field Hin is generated by the magnetostatic coupling between the fixed magnetic layer and the free magnetic layer (topological coupling), it causes a problem such that the ferromagnetic coupling magnetic field becomes stronger, and an asymmetry of a reproducing waveform is increased.